Foundation Stabilization System and Method of Use

ABSTRACT

A system for stabilizing moisture content of soil adjacent a building foundation uses a French drain which is dug around a perimeter of the building and grey water produced in the building as a source of irrigating fluid. Grey water sources from within the building are directed to the French drain through conduits which are separate from the normal sewage lines leading to the sanitary sewer system. An overflow conduit diverts any excess overflow from the French drain to the sanitary sewer line.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The present invention relates generally to a method for controlling and stabilizing the moisture content of soil around and beneath the foundation of a building, such as a residential building structure, particularly where the structure is located on expansive soils.

B. Description of the Prior Art

As is well known in the civil engineering arts, foundation soils expand and contract to a greater or lesser degree according to the moisture content of the soils. While soil shrinkage and expansion can be a problem in any geographical area, those area having a high clay content are especially vulnerable. Certain types of soil, such as the clay soils of parts of the South, Southwest and Mid-western regions, for example, can expand many orders of magnitude with the addition of sufficient moisture content. These clays may have a high montmorillinite content which causes the soils to have the extreme expansive characteristics. In the South and Southwest, the so-called “black gumbo” soils continually expand and contract, depending upon the moisture content of the soils.

One can readily see that buildings may be damaged by such expansion and contraction of the soils surrounding and beneath the foundation. Damage of this type to foundations results in large expenditures on the part of homeowners each year. Repeated wetting and drying of the soil, particularly when done unevenly, can place great stress on the foundations resulting in tilting, cracking and even ultimate destruction of the foundation. This, of course, often results in damage to structures supported on such foundations.

It is believed that many instances of building foundation stress in these situations is a result of migration of moisture from beneath the perimeter of the beams of the foundation, with resulting shrinkage of the soils and a loss of soil support at the perimeter of the foundation. This shrinkage occurs after extended periods of dry weather, such as that which is common to the summer months in the South, Southwest and Midwest regions of the United States. The loss of moisture from the soil surrounding the foundation causes moisture in the protected area under the foundation to migrate into the depleted surrounding soil. This reduction of moisture content of the soil under the edges of the foundation causes the soil to contract and move away from the foundation. At the very least, the soil beneath the foundation goes up and down in overall volume, thereby causing the foundation, masonry and interior sheetrock to be ruptured or cracked. In more serious cases, door structures and window structures may be cracked and serious distresses may be induced into the structure of the building itself.

When the normal fall and winter rains replenish the soil moisture, the cycle is reversed. Moisture then migrates back under the foundation perimeter, swelling the supporting clays and moving the perimeter beams in a vertically upward direction. The perimeter of the foundation will continue to move up and down with the seasonal cycle with the magnitude of movement varying with the extremes of the wet-dry weather cycles.

To solve these problems, a variety of remediation and repair techniques have been used and the results vary widely. One technique is to utilize a massive slab and beam structure, or a series of concrete “piers”, which will not fail as the soil shrinks and expands. Although, in some instances, these techniques may be successfully utilized, they are undesirable in that they are often times inordinately expensive and increase the construction costs in these structures. In addition, this technique cannot be used on existing foundations.

A second technique is to attempt to repair the damage to the existing foundations by grouting the cracks formed in the foundation due to the shrinking and swelling of the soil. These attempts may actually act to increase the damage to the foundation when the cycle is reversed in that the foundation cannot return to its original position because of grout material in the crack.

Other techniques have included attempts to stabilize the expansive soil present under a foundation. Stabilization techniques utilize lime slurry material which is injected into the soil under high pressure. The effectiveness of the use of this lime material is variable and believed to be a result of a chemical reaction that takes place between lime and clay whereby some types of clay particles are significantly altered and reduced in plasticity and increased in mechanical strength. It was believed that this chemical reaction could be achieved throughout the soil by mixing lime with the soil under the foundation. However, it has been found that such mixing is very limited. The process can be quite expensive and the results are not always predictable.

Another technique was the use of a surface or subsurface irrigation system positioned around the foundation to control the moisture content of the soil under the foundation. These early systems were nothing more than simple soaker hose, drip irrigation systems laid on top of the ground surrounding the foundation and controlled by an individual on an as-needed/as-remembered basis. More elaborate systems were also devised in which permeable hoses or pipe similar to the type used in lawn irrigation systems are placed in the soil of the foundation. A low head pressure of water was then connected to the pipes causing water to slowly percolate into the soil supporting the foundation. The irrigation system can be placed adjacent to the edge of the foundation and moisture sensors imbedded around the house to control the operation of the system. These types of systems may be relatively successful in attacking the problem of uneven moisture in the surrounding soils, but they have the disadvantage of using water from the City main or other pressurized water source in order to make the systems function. This can result in the use of a fairly large amount of City water each year and adds to the problem of an ever decreasing water table level in many parts of the country.

Thus, prior art systems for stabilizing moisture content of soil around and beneath the foundation of a building leave much to be desired. Although they may operate with limited success, the prior art systems are not uniformly effective and efficient. Perhaps equally important, many of the prior art systems used water from the City water system, or from the homeowner's private well, as the source of irrigation water for the system. This was costly and environmentally unfriendly in many respects. Substantial improvements are thus need in the area of foundation stabilization systems.

SUMMARY OF THE INVENTION

A method is shown for stabilizing the moisture content of soil around and beneath the foundation of a building where the foundation is surrounded by a soil perimeter, the building also having a plurality of sources of grey water produced in the building and a sanitary sewer conduit which receives sewage from the building. A French drain is dug in the soil around the complete outside perimeter of the foundation. The French drain includes a perforated conduit which is buried in a surrounding particulate drainage material. The particulate drainage material is contained in a trench dug around the perimeter of the building foundation. The perforated conduit is pervious to water, allowing water from the perforated conduit to pass through the particulate drainage material and to enter the surrounding soil.

Grey water produced within the building is directed through a plurality of grey water conduits to the perforated conduit of the French drain, whereby grey water is directed outwardly from the French drain into the soil surrounding the foundation of the building. Any sewer water which is produced within the building is directed through separate fluid conduits to the sanitary sewer conduit.

In the typical case, the building is a residential dwelling structure where the building foundation is situated on a surrounding strata comprised at least in part of expansive clay. The source of the grey water can be, for example, selected from among the group consisting of water from a laundry sink, water from a clothes washer, water from a lavatory, water from a tub and water from a shower in the building.

The perforated conduit is connected to the sanitary sewer conduit at at least one point by an overflow conduit. The overflow conduit has a check valve contained therein which accepts an excess of grey water produced in the building structure, but which prevents sewage in the sanitary sewer from reentering the grey water conduit or perforate conduit through the check valve. The check valve can be, for example, a rubber duck bill valve which opens in response to the flow of grey water only.

The particulate perforate material can be selected from among the group consisting of sand, gravel and rock. The particulate perforate material, contained in the trench which is dug around the perimeter of the building foundation, is enveloped in a fabric material which helps to prevent the infiltration of soil into the perforate material but which allows the egress of water from the particulate material into the surrounding soil.

A sheet of plastic material forms a deflector sheet of a predetermined width which extends outwardly from the building foundation over the French drain and into the surrounding soil. As a result, any rain water which runs off the building roof is directed away from the French drain and outwardly toward the surrounding soil to prevent flooding of the French drain.

Additional objects, features and advantages will be apparent in the written description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is a simplified view of a typical building, in this case a residential structure, shown in an elevated view to illustrate the placement of the surrounding perforated conduit and connecting grey water lines which make up a portion of the foundation stabilization system of the invention.

FIG. 2 is a simplified piping schematic of the system of the invention which uses grey water from a building to maintain a constant moisture content in the soil surrounding the building foundation.

FIG. 3 is a partial, sectional view of a portion of the building foundation of the building shown in FIG. 1 showing the placement of the component parts of the system of the invention.

FIG. 4 is an isolated view of a portion of the sanitary sewer conduit of the building, the sewer conduit being connected to the perforated conduit which surrounds the building foundation by an overflow conduit, the overflow conduit also containing a check valve.

DETAILED DESCRIPTION OF THE INVENTION

The preferred version of the invention presented in the following written description and the various features and advantageous details thereof are explained more fully with reference to the non-limiting examples included in the accompanying drawings and as detailed in the description which follows. Descriptions of well-known components and processes and manufacturing techniques are omitted so as to not unnecessarily obscure the principle features of the invention as described herein. The examples used in the description which follows are intended merely to facilitate an understanding of ways in which the invention may be practiced and to further enable those skilled in the art to practice the invention. Accordingly, the examples should not be construed as limiting the scope of the claimed invention.

In describing the present invention, reference will be had to the terms “black water” and “grey water.” “Black water” is a term dating back until at least the 1970's used to describe water which contains fecal matter and urine. It is also referred to as brown water, foul water or sometimes simply as sewage. It is distinct from “grey water,” or sullage, which is generally understood to be the residue from washing processes. Thus, water coming from domestic equipment, other than toilets, e.g., bathtubs, showers, sinks, etc., is generally referred to as “grey water.” It is preferably kept separate from black water, e.g., which comes primarily from toilets. Separation of black water and grey water is commonly employed in new construction today and is present in almost all new “ecological” buildings.

Turning now to FIG. 1 of the drawings, there is shown a building, in this case a typical residential dwelling designated generally as 11. The building 11 has a roof 18, sidewalls 19 and a foundation 21. The building is shown in phantom lines and in an elevated manner in order to more clearly illustrate the foundation moisture control system of the invention which includes the French drain 13 and plurality of grey water conduits 15, as will be explained in greater detail. The foundation of the building 11 is surrounded by a soil perimeter (shown generally at 17 in FIG. 3). FIG. 3 also shows a section of the building wall 19 supported on the concrete foundation 20 which is separated from a sand fill 20 by a plastic vapor barrier material 22.

FIG. 2 is intended to be representative of a plumbing layout of a typical residential dwelling structure. While the invention will be described with respect to a residential dwelling structure, it will be understood that the principles employed could be utilized in the case of a commercial building structure, or any other suitable structure where the foundation is built upon expansive soils. With reference to FIG. 2, the particular plumbing arrangement of the building includes a laundry sink 23, a washer 25, a kitchen sink 27, a dishwasher 29, a pair of lavatories 31, 37, a tub 35, a pair of toilets 33, 39, and a shower 41. As shown in FIG. 2, the sewage, sometimes referred to as “black water” is directed through sewer conduits 43, 45 and 47 to the sanitary sewer line 49 outside the structure.

With reference now to FIGS. 2 and 3, the foundation stabilization system of the invention utilizes a “French drain” which is dug around the complete outside perimeter of the foundation. A French drain, rubble drain, rock drain, drain tile, perimeter drain or land drain will be familiar to those skilled in the relevant arts and is a term used to describe is a trench covered with gravel or rock that redirects surface and groundwater away from an area. French drains are often provided with perforated hollow pipes along the bottom to quickly vent water that seeps down through the upper gravel or rock. French drains are common drainage systems, primarily used to prevent ground and surface water from penetrating or damaging building foundations. The typical use of the French drain is therefore opposite to the use to be described in the instant building foundation stabilization system. That is, the prior art use was typically to direct water away from the foundation, basement, etc. However, in the present invention, the French drain is used to direct water toward the soil immediately adjacent the building foundation.

As best seen in FIG. 3, the French drain 51 includes a perforated conduit 53 which is buried in a surrounding particulate drainage material 55. The perforated conduit can be, for example, a 4 inch diameter PVC pipe which has been perforated on at least the bottom side. The particulate drainage material 55 is contained in a trench dug around the perimeter of the building foundation and can be any conveniently available fill material which has the requisite permeability to water, for example, sand, gravel or rock. The particulate material 55, being pervious to water, allows water from the perforated conduit 53 to pass through the particulate drainage material and to enter the surrounding soil 17.

The preferred French drain also includes a filter fabric 57 which surrounds or envelops the particulate drainage material 55. This can be, for example, a treated cloth or plastic mesh material which helps to prevent the infiltration of soil into the particulate drainage material but which allows the egress of water from the particulate material into the surrounding soil.

As shown in FIG. 3, a deflector sheet 59 of a predetermined width extends outwardly from the building foundation 20 over the French drain 51 and into the surrounding soil 17, whereby rain water which runs off the building roof is directed away from the French drain and outwardly toward the surrounding soil to prevent flooding of the French drain. The deflector sheet in the example illustrated is 6 mil thick sheet of roll plastic.

As shown in FIG. 2, the perforated conduit 53 is connected to various sources of “grey water” within the building structure by a plurality of grey water conduits, such as conduits 63, 65, 67, 69 and 71.The grey water conduits allow grey water being discharged from within the building to be directed to the perforated conduit of the French drain, whereby grey water is directed outwardly from the French drain into the soil surrounding the foundation of the building. Any sewer water produced in the building continues to be discharged through the separate fluid conduits 43, 45 and 47, to the sanitary sewer conduit 49. The source of the grey water can thus comprise a source selected from among the group consisting, for example, of water from a laundry sink, water from a clothes washer, water from a lavatory, water from a tub and water from a shower in the building. The sewage source can be, for example, from a building toilet, dishwasher, or the like.

In the preferred foundation stabilization system of the invention, the perforated conduit 53 is connected to the sanitary sewer conduit 49 at at least one point by an overflow conduit (73 in FIGS. 2 and 4). The overflow conduit 73 is preferably provided with some sort of check valve 75 which will accept an excess of grey water produced in the building structure, but which prevents sewage in the sanitary sewer from reentering the grey water conduit or perforate conduit through the check valve. This would be convenient, for example, in the situation where the owners of the dwelling have an unusual number of guests which temporarily overloads the grey water discharge. In the particular example illustrated, the check valve 75 is a rubber duck bill valve which opens in response to the flow of grey water only.

An invention has been provided with several advantages. The foundation stabilization system of the invention is relatively simple in design and economical to implement. It takes advantage of the separation of black water and grey water to provide water to the building foundation which would otherwise be wasted. The average person is estimated to use 8-100 gallons of water per day in a typical household. This would be 320 gallons of water each day for a typical family of four. Subtracting 80 gallons a day for toilets, this leaves some 240 gallons of water which can be put back into the soil using the foundation stabilization system of the invention. The municipality is now required to supply only about ¼ of the water requirement that was previously needed. The system also increases the amount of water going back to the aquifer, providing a natural filter for the water, and also cutting down on run-off.

While the invention has been shown in one of its forms, it is not thus limited and is susceptible to various changes and modifications without departing from the spirit thereof. 

I claim:
 1. A method for stabilizing moisture content of soil around and beneath the foundation of a building where the foundation is surrounded by a soil perimeter, the building also having a plurality of sources of grey water produced in the building and a sanitary sewer conduit which receives sewage from the building, the method comprising the steps of: constructing a French drain in the soil around the complete outside perimeter of the foundation, the French drain including a perforated conduit which is buried in a surrounding particulate drainage material, the particulate drainage material being contained in a trench dug around the perimeter of the building foundation, the perforated conduit being pervious to water, allowing water from the perforated conduit to pass through the particulate drainage material and to enter the surrounding soil; directing grey water produced within the building through a plurality of grey water conduits to the perforated conduit of the French drain, whereby grey water is directed outwardly from the French drain into the soil surrounding the foundation of the building; and directing any sewer water produced in the building through separate fluid conduits to the sanitary sewer conduit.
 2. The method of claim 1, wherein the building is a residential dwelling structure.
 3. The method of claim 1, wherein the building foundation is situated on a surrounding strata comprised at least in part of expansive clay.
 4. The method of claim 1, wherein the source of the grey water is selected from among the group consisting of water from a laundry sink, water from a clothes washer, water from a lavatory, water from a tub and water from a shower in the building.
 5. The method of claim 1, wherein the perforated conduit is connected to the sanitary sewer conduit at at least one point by an overflow conduit, the overflow conduit having a check valve contained therein which accepts an excess of grey water produced in the building structure, but which prevents sewage in the sanitary sewer from reentering the grey water conduit or perforate conduit through the check valve.
 6. The method of claim 1, wherein the check valve is a rubber duck bill valve which opens in response to the flow of grey water only.
 7. The method of claim 1, wherein the particulate perforate material is selected from the group consisting of sand, gravel and rock.
 8. The method of claim 1, wherein the particulate perforate material which is contained in the trench which is dug around the perimeter of the building foundation is enveloped in a fabric material which helps to prevent the infiltration of soil into the perforate material but which allows the egress of water from the particulate material into the surrounding soil.
 9. The method of claim 8, wherein the building has a building roof which directs rainfall water downwardly, and wherein a deflector sheet of a predetermined width extends outwardly from the building foundation over the French drain and into the surrounding soil, whereby rain water which runs off the building roof is directed away from the French drain and outwardly toward the surrounding soil to prevent flooding of the French drain.
 10. The method of claim 9, wherein the deflector sheet is a sheet of roll plastic. 